Ecological National Synthesis (ENS) Project

Four Primary Objectives of the ENS Project:

Assess the status and trends of aquatic ecological conditions (invertebrates, fish, algae and habitat) in rivers and wadeable streams.

Relate ecological conditions to chemical stressors (such as nutrients and pesticides), physical disturbances (such as habitat and hydrologic alterations) in the context of different environmental settings and land uses.

Enhance understanding of factors that influence the biological integrity of streams and how these stream ecosystems may respond to diverse natural and human factors.

Develop key ecological indicators of aquatic health.

Estimation
and application of indicator values for common macroinvertebrate genera
and families of the United States

ABSTRACT.- Tolerance of macroinvertebratetaxa to chemical and physical stressors are widely
used in the analysis and interpretation of bioassessment
data, but many estimates lack empirical bases. Our main objective was to
estimate genus- and family-level indicator values (IVs) from a data set of macroinvertebrate communities, chemical, and physical
stressors collected in a consistent manner throughout the United States.
We then demonstrated an application of these IVs to detect alterations in
benthic macroinvertebrate assemblages along gradients
of urbanization in New England and Alabama.
Principal components analysis (PCA) was used to create synthetic gradients of
chemical stressors, for which genus- and family-level weighted averages (WAs) were calculated. Based on results of PCA, WAs were
calculated for three synthetic gradients (ionic concentration, nutrient
concentration, and dissolved oxygen/water temperature) and two uncorrelated
physical variables (suspended sediment concentration and percent fines).
Indicator values for each stress gradient were subsequently created by
transforming WAs into ten ordinal ranks based on
percentiles of values across all taxa. Mean IVs of
genera and families were highly correlated to road density in Alabama
and New England, and supported the conclusions
of independent assessments of the chemical and physical stressors acting in
each geographic area. Family IVs were nearly as responsive to urbanization as
genus IVs. The limitations of widespread use of these IVs are discussed.